The hospitals have apologised and paid a "five-figure sum" to his parents.

The letter sent to the Hunt family, of Thornton-Cleveleys in Lancashire, by the chief executives of both hospitals said it is "a matter of deep regret" that Daniel's death was not prevented.

The risk that Daniel "might experience a life threatening and sudden deterioration was not appreciated to the extent that it ought to have been," it said.

A joint statement from both hospitals said investigations "concluded that additional steps could have been taken during the course of his admission to both hospitals to further stabilise and improve his condition".

Diane Rostron, the specialist medical solicitor who represented the family, said Blackpool Victoria children's unit were aware of Daniel's condition and complications that can arise.

He was admitted after being sick at home but staff did not recognise his deteriorating condition, she said.

And there were delays in transferring him to Manchester, where there was a failure to escalate his treatment.

Ms Rostron said the Hunts did not want to sue the hospitals but were forced to because they would not accept any responsibility for their son's death.

After initially denying substandard care, the hospitals admitted liability in October before the first court hearing was due to take place.

Graham Hunt said: "I didn't think for one moment I'd be taking my son in and not bringing him out for something that would have been treatable with the proper people to look after him - and they didn't," he said.

Ms Rostron said: "The simple fact is, this was an avoidable death."

"It has heaped insult on top of injury... they should have admitted this as soon as the coroner's inquest was concluded.

"As every day has gone by the parents have been caused increasing amounts of pain."